JPS5858667B2 - Liquid developer for electrostatography - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to improvements in binders used in electrostatographic liquid developer toners.

General liquid developers for electrostatic photography mainly consist of a colorant made of carbon black, an organic pigment, or an organic dye, and a binder made of synthetic or natural resins or resins such as acrylic resin, phenol-modified alkyd resin, rosin, or synthetic rubber. A toner containing a polarity control agent such as lecithin, metal soap, linseed oil, or higher fatty acid is dispersed in a highly insulating and low dielectric constant solvent such as a petroleum-based aliphatic hydrocarbon. .

During the development process, such toner undergoes electrophoresis in accordance with the charge of the electrostatic latent image formed on the surface layer of the electrophotographic photosensitive material or electrostatic recording material, and adheres to that area to form an image. However, in conventional liquid developers, the resin and polarity control agent diffuse into the carrier liquid over time, causing agglomeration and making the polarity unclear, resulting in poor image quality.
In particular, in addition to the problem of significant deterioration of image density, toner adhesion and therefore image fixation are weak, so when used in color electrophotography, the four colors of yellow, red, blue, and black are unevenly layered. Therefore, it is impossible to reproduce faithful colors, and if an image is formed on zinc oxide photosensitive paper and used as an offset master for offset printing, the number of sheets to be printed does not increase, and printing defects may occur. There is.

A first object of the present invention is to provide an electrostatographic liquid developer capable of forming high quality images by improving the storage stability of the toner.

The second object of the present invention is to provide a liquid developer for electrostatography that can solve the problems of color reproduction in color electrophotography and the problems of printing durability and printing defects in offset printing by improving the adhesion of toner. It is to provide.

That is, the developer of the present invention is an electrostatographic liquid developer comprising a toner mainly composed of a colorant and a binder resin dispersed in a carrier liquid comprising a petroleum-based aliphatic hydrocarbon or a halogenated aliphatic hydrocarbon. As a binding resin, in a petroleum-based aliphatic hydrocarbon or halogenated aliphatic hydrocarbon solvent, the general formula % [where R is hydrogen or a methyl group, A is COOCnH2n+1, or -0COCnH2n+t]
(However, n is an integer of 6 to 20).

] monomer (monomer A), polyfunctional acrylic ester and/or polyfunctional methacrylic ester (monomer B), unsaturated carboxylic acid, unsaturated carboxylic acid anhydride, unsaturated nitrogen-containing compound, glycidyl group Containing unsaturated compounds, alkyl acrylates (1 to 1 carbon atoms)
5) Contains a cross-linked copolymer obtained by polymerizing at least one type of hetamine (monomer C) selected from the group consisting of esters and/or alkyl methacrylates (having 1 to 5 carbon atoms). This is a characteristic feature.

To prepare the copolymer used in the present invention, monomer A represented by the above general formula, monomer B, and monomer C are mixed in a solvent containing petroleum-based aliphatic hydrocarbon or halogenated aliphatic hydrocarbon as the main component. The polymerization may be carried out by heating in the presence of a polymerization initiator such as benzoyl peroxide or azobisisobutyronitrile.

Through this reaction, a copolymer having a three-dimensional structure in which the three components of monomers A, B, and C are crosslinked to each other in a network form is obtained.

Note that this crosslinking is caused by the polyfunctionality of Nanatsumer-B.

Monomer A used in this reaction has the property of being solvated with the solvent both before and after polymerization, and monomer B has the property of being solvated with the solvent before polymerization but not solvating after polymerization. Monomer C has the property that it is solvated with the solvent before polymerization, but becomes insoluble in the solvent after polymerization.

Therefore, the copolymer thus obtained is in a dispersed state in the solvent.

The monomer A component in the copolymer contributes to the dispersion stability (therefore storage stability) and adhesiveness of the toner, and the monomer C component generally belongs to polar monomers and contributes to the polarity and dispersion stability of the toner.

Note that the ratio of monomer A: monomer B: monomer C is 20
Approximately 90:1 to 20:1 to 50 (by weight) is appropriate.

In the present invention, silica fine particles, wax or polyolefin having a softening point of about 60 to 130°C can be added to the copolymer manufacturing process.

When fine silica particles are used, it is thought that the copolymer is obtained with the fine silica particles incorporated in its network structure.

In this case, it is thought that the silica itself will not undergo physical changes such as dissolution during the reaction.

In any case, in the case of silica, specific gravity is the dispersion medium.

resembling an aliphatic hydrocarbon or its halide;
By preventing gelation of the copolymer, dispersion stability can be further improved.

On the other hand, when wax or polyolefin is used, these are dissolved in the reaction system due to the axial heat during the polymerization reaction, but after the reaction, they are precipitated into particles by cooling, and the copolymer is obtained in a state that is adsorbed to these fine particles. It is considered that it can be received.

Here, wax or polyethylene has a specific gravity similar to that of the dispersion medium, prevents gelation of the copolymer, and has a molecular structure similar to that of the dispersion medium, so it not only helps improve dispersion stability but also has a low softening point. Therefore, it also helps improve adhesion.

The amount of silica, wax or polyolefin added is suitably about 5 to 50 parts by weight per 100 parts by weight of the copolymer.

To make a liquid developer using the copolymer thus obtained, generally 1 part by weight of the colorant is mixed with 0.3 to 3 parts by weight of the copolymer, and this is mixed with petroleum-based aliphatic hydrocarbon or halogen. In the presence of 10 to 20 parts by weight of aliphatic hydrocarbon carrier liquid, sufficiently disperse with a dispersing machine such as an attritor, ball mill, or kedimir to obtain a concentrated toner, which is then diluted 5 to 10 times with a similar solvent. do it.

In this case, the copolymer dispersion obtained as described above can be used as is as the copolymer and solvent.

Further, when preparing a concentrated toner, other resins other than the copolymer of the present invention and a polarity control agent such as metal soap may be added to the mixture as necessary.

Since the developer thus obtained has a low viscosity, it is easy to handle, has the advantage of being sufficiently absorbent when toner is supplied to a copying machine, and is hard to harden even when stored for a long period of time.

Next, the materials used in the present invention will be explained.

First, specific examples of monomer A include lauryl methacrylate, lauryl acrylate, stearyl methacrylate, stearyl acrylate, 2-ethylhexyl methacrylate, 2-ethylhexyl acrylate, dodecyl methacrylate, dodecyl acrylate, hexyl methacrylate, hexyl acrylate, octyl methacrylate, octyl Examples include methacrylate, cetyl acrylate, cetyl acrylate, vinyl laurate, and vinyl stearate.

Examples of monomer B include ethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, diethylene glycol methacrylate, triethylene glycol triacrylate, triethylene glycol triacrylate, butanediol diacrylate, butanediol dimethacrylate, 1,6- hexanediol diacrylate, 1
゜6-hexanediol diacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, tetramethylolmethane triacrylate, tetramethylolmethane triacrylate,
Tetramethylolmethanetetraacrylate, tetramethylolmethanetetramethacrylate, dipropylene glycol diacrylate, dipropylene glycol dimethacrylate, trimethylolhexane triacrylate, trimethylolhexane trimethacrylate, pentaerythritol tetraacrylate, pentaerythritol tetramethacrylate, 1, Examples include 3-butylene glycol diacrylate, 1,3-butylene glycol dimethacrylate, trimethylolethane triacrylate, and trimethylolethane methacrylate.

Examples of unsaturated carboxylic acids and their anhydrides in the C group monomer include acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid, crotonic acid, aconitic acid, cinnamic acid, and their anhydrides.

Examples of unsaturated nitrogen-containing compounds of group C monomers include vinylpyrrolidone, 2-vinylpyridine, 4-vinylpyridine, N-vinylpyridine, N-vinylimidazole, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, etc. Examples of the alkyl (carbon number 1 to 5) ester of acrylic acid or methacrylic acid in the C group monomer include methyl acrylate,
Examples include methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate, and butyl methacrylate.

Further, typical examples of unsaturated compounds containing a glycidyl group among the monomers of Group C include glycidyl acrylate and glycidyl methacrylate.

Polymerization initiators used when polymerizing these monomers A, B, and C include benzoyl peroxide, t-butyl perbenzoate, cyamyl peroxide, di-t-butyl peroxide, lauryl peroxide, and azobisisobutyl peroxide. Lonitrile can be used.

Petroleum-based, aliphatic hydrocarbons or halogenated aliphatic hydrocarbons used in the present invention include kerosene, ligroin, n
-hexane, n-pentane, n-hebutane, n-octane, i-octane, i-dodecane, i-nonane (commercially available products include Exxon's Isopar H, G, L; naphtha/166, (Shell Sol, manufactured by Shell Oil Co., Ltd.), carbon tetrachloride, perfluoroethylene, etc.

These aliphatic hydrocarbons or halogenated aliphatic hydrocarbons are solvents with high insulation properties (electrical resistance of 11010 Q-a or more) and low dielectric constants (dielectric constant of 3 or less).

Moreover, a small amount of aromatic solvents such as benzene and toluene can also be added to these aliphatic solvents.

Also, wax or poly with a softening point of 60 to 130°C.

Specific examples of commercially available olefins are as follows.

Coloring agents include carbon black, oil blue alkali blue, fuclocyanine blue, phthalocyanine green, spirit black, aniline black, oil violet, benzidine yellow, methyl orange,
Examples include dyes or pigments such as brilliant carmine, fast red, and crystal violet.

Examples of other resins include acrylic resins, ester gums; natural resins such as hardened rosin; and maleic acid resins modified with these natural resins, phenol resins, polyesters, pen erythritol resins, and the like.

As polarity control agents, metal soap, lecithin, linseed oil,
Common examples include higher fatty acids.

Production examples and examples of copolymers are shown below.

Production Example 1 0300 g of Isopar was placed in a 21 flask equipped with a stirrer, a thermometer, and a reflux condenser, and heated to 90°C.

In this, lauryl methacrylate 1.170g, methacrylic acid 10g, diethylene glycol dimethacrylate 3.
A solution consisting of B? A combined dispersion was obtained.

Note that the particle size of the copolymer was 4 to 5 μm.

Production Example 2 250 g of the copolymer dispersion obtained in Production Example 1 was mixed with 2 (l) of polyethylene (DYNF manufactured by Union Carbide) in a flask, heated and dissolved at 110°C for 3 hours, and then cooled to obtain a solution with a viscosity of 220 cp. A copolymer-polyethylenef dispersion was obtained.

Note that the particle size of this mixed system was 1 to 3 microns.

Production Example 3 Take isooctane 301 in the same container as Production Example 1, and add 90
heated to ℃.

Next, a solution consisting of 170 g of cetyl methacrylate, 20 g of triethylene glycol dimethacrylate, 10 g of N-vinylpyridine, and 5 g of azobisisobutyronitrile was added dropwise to this over 1 hour to cause a polymerization reaction.
The reaction was completed by heating at 5° C. for 3 hours.

A copolymer dispersion having a polymerization rate of 96.8% and a viscosity of 180 cp was thus obtained. The particle size of the copolymer was 2 to 3 microns.

Production Example 4 The copolymer dispersion 251 obtained in Production Example 3 was mixed with 18 g of bleached beeswax in a flask, heated and stirred at 1.00°C for 2 hours, and then cooled to obtain a copolymer with a viscosity of 161 cp. A bleached beeswax mixed dispersion was prepared.

Note that the particle size of this mixed system was 0.5 to 1.0 μm.

Production Example 5 In the same container as Production Example 1, add 300 g of isooctane and particle size 1.
10 g of ~3μ silica powder was taken and heated to 95°C.

In this, 150 g of 2-ethylhexyl methacrylate,
15 g of 1,6-hexane gelicol dimethacrylate,
A solution consisting of 28 g of glycidyl methacrylate, 25 g of styrene, and 5 g of abbisisobutyronyl
After the dropwise addition and polymerization reaction took place over a period of time, the reaction was further stirred at 95° C. for 2 hours to complete the reaction.

In this way, a copolymer-silica mixed dispersion having a polymerization rate of 98.2% and a viscosity of 106 cp was obtained.

The particle size of this mixed system was 3 to 5 microns.

Production Example 6 300 g of Eye Tuber L and 30 g of polyethylene (Sunwax 131-P) were placed in the same flask as in Production Example 1, and heated to 95°C.

Next, a solution consisting of 150 g of stearyl methacrylate, 21 g of tetramethylolmethanetetraacrylate, 10 g of ichconic acid, 30 g of methyl methacrylate, and 5 g of lauryl peroxide was added dropwise to the solution over a period of 1 hour at the above temperature, followed by a polymerization reaction. The reaction was completed by heating at room temperature for 3 hours.

In this way, a mixed copolymer/polyethylene dispersion having a polymerization rate of 98.2% and a viscosity of 165 cp was obtained.

The particle size of this mixed system was 5 to 8 microns.

Example 1 Carbon blank (Mitsubishi Carbon MA-11) 10g Resin dispersion obtained in Production Example 1 50g Kerosene 10
0 g was dispersed in a Kedimill for 6 hours to obtain a concentrated toner with a viscosity of 16.8 cp, and 10 g of the concentrated toner was dispersed in kerosene 11 to prepare an electrostatic photographic liquid developer.

Next, this developer was placed in a commercially available electrophotographic copying machine and copies were made on commercially available zinc oxide photosensitive paper, resulting in copies with an image density of 1.32 and an image fixation rate of 86.6%.

The fixing rate (%) was also determined from the formula:

Example 2 Carbon black (Raben 14 manufactured by Columbia Carbot) 15.9 Copolymer obtained in Production Example 2 ~ Polyethylene mixed resin dispersion 1009 Kerosene
100 g of manganese naphthenate (1 g) was treated in the same manner as in Example 1 to prepare an electrostatic photographic liquid developer.

The viscosity of the concentrated toner was 10.3 cp.

Next, using this developer, copies were made in the same manner as in Example 1, and copies with an image density of 1630 and an image fixation rate of 86.6% were obtained.

Example 3 Carbon black (Raben 5250 manufactured by Columbia Carbon) 15g Resin dispersion obtained in Production Example 3 100g
Rosin 1
00.9 Shi Chin
3 g was treated in the same manner as in Example 1 to prepare a liquid developer.

The viscosity of the concentrated toner was 18.0. After making a copy in the same manner as in Example 1, it was subjected to a desensitizing process and used as an offset master for offset printing.
A printing durability of 20,000 sheets was obtained.

The image fixation rate of the copy (therefore, the offset master) was 86.0%.

Example 4 Benzidine Yellow (manufactured by Inu Nisseika Co., Ltd.) 30g
Copolymer obtained in Production Example 4 - Exposed beeswax mixed resin dispersion 70g
Shin 100.
? Example 1 5g of nickel naphthenate
A liquid developer for color electrostatic photography was prepared in the same manner as above.

The viscosity of the concentrated toner was 46.1 cp.

Next, put this developer into a commercially available color electrophotographic copying machine,
When color copying was performed on commercially available zinc oxide photosensitive paper, a clear color image was formed.

Example 5 Carbon black (MA-11 manufactured by Mitsubishi Carbon Co., Ltd.) 20. ! ;' The copolymer obtained in Production Example 5 - 130.9 g of silica mixed system and 100 g of kerosene were treated in the same manner as in Example 1 to prepare a liquid developer for electrostatic photography.

The viscosity of concentrated toner is 20. At Ocp. Ivy.

Thereafter, copies were made in the same manner as in Example 1, and copies with an image density of 1.35 and an image fixation rate of 86.3% were obtained.

After storing this concentrated toner at room temperature for 3 months, the viscosity was measured and found to be 28.2 cp, with little toner sedimentation.When copies were made in the same manner, the image density was 1.30 cp.
Copies with a fixation rate of 88.0% were obtained.

Claims (1)

[Scope of Claims] 1. An electrostatographic liquid developer comprising a toner containing a colorant and a binder resin as main components dispersed in a carrier liquid consisting of a petroleum-based aliphatic hydrocarbon or a halogenated aliphatic hydrocarbon. , as the binding resin, in a petroleum aliphatic hydrocarbon or halogenated aliphatic hydrocarbon solvent, the general formula % formula % [where R is hydrogen or a methyl group, A is COOCnH2n+s, or -OCOCn H2n
+t (where n is an integer from 6 to 20), respectively. ] monomer (monomer A), polyfunctional acrylic ester and/or polyfunctional methacrylic ester (monomer B), unsaturated carboxylic acid, unsaturated carboxylic acid anhydride, unsaturated nitrogen-containing compound, glycidyl At least one monomer (monomer C) selected from the group consisting of a group-containing unsaturated compound, an alkyl acrylate (alkyl having 1 to 5 carbon atoms) ester, and/or an alkyl methacrylate (1 to 5 carbon atoms) ester; 1. A liquid developer for electrostatic photography, comprising a crosslinked copolymer obtained by polymerization.